Sustainable dye removal using PANI-salt functionalized potato peels in a fixed-bed column: Optimization and modeling

Abstract

This study investigates a practical and low-cost approach for the removal of multiple dyes (Basic Fuchsin (BF), Methylene Blue (MB), Malachite Green (MG), Rhodamine B (RhB), Congo Red (CR), and Bordeaux B (BB)) from aqueous solutions using dynamic fixed-bed adsorption. Native potato peels (PP), a biodegradable biosorbent, were chemically modified with polyaniline in its emeraldine salt form (PANI-ES) to enhance adsorption performance. The optimal operational parameters were as follows: dye concentration of 30 mg/L, bed height of 8 cm, particle size of 1 mm, flow rate of 7.5 mL/min, and pH 6.5. The adsorption capacity of unmodified PP correlated inversely with dye molecular weight, while PANI-ES grafting significantly extended breakthrough times from 356 to 400.18 min for BF, 219 to 387.68 min for MB, 96.2 to 373.3 min for MG, 141.62 to 359.15 min for RhB, and 68.1 to 363.52 min for CR, achieving maximum dye removal efficiencies of 99.67 % (BF), 99.88 % (MB), 98.01 % (MG), 94.41 % (RhB), and 92.08 % (CR), respectively. The developed biosorbent was characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, and X-ray diffraction (XRD). Breakthrough data were fitted using the Adams–Bohart, Thomas, Yoon–Nelson, and bed depth service time (BDST) models, highlighting the potential of PANI-functionalized agro-waste for efficient and sustainable wastewater treatment.